1. Field
The present disclosure relates generally to aircraft and, in particular, to a method and apparatus for controlling aerodynamic performance of an aircraft. Still more particularly, the present disclosure relates to a method and apparatus for changing the shape of an airfoil for an aircraft.
2. Background
An aircraft is a type of vehicle capable of flying through the atmosphere. Aircraft may include fixed wing aircraft and rotor craft. The flight of an aircraft may be controlled by a number of airfoils. An airfoil is a part that may provide aerodynamic performance for an aircraft. An airfoil may be, for example, a wing or blade. The design and shape of airfoils may generate lift, control stability, change direction, change drag, and/or change other suitable aerodynamic parameters for an aircraft.
Flight control surfaces on an airfoil of an aircraft may be used to change the direction of an aircraft around three axes. These axes include a vertical axis, a longitudinal axis, and a lateral axis. A vertical axis passes through an aircraft from top to bottom. Rotation or movement about this axis is called yaw. Yaw changes the direction of the nose of an aircraft pointing it to the left or right. The longitudinal axis passes through the aircraft from the nose to the tail. Rotation about this axis is referred to as bank or roll. The lateral axis passes from one wing tip of an aircraft to another wing tip of an aircraft. Rotation about this axis is referred to as pitch.
Different control surfaces such as, for example, an aileron, an elevator, a rotor, a trim, a rudder, a spoiler, a flap, a slat, or other suitable control surfaces may be moved to change the shape of an airfoil to provide for different axes of motion for the aircraft. These control surfaces may be used to optimize the aerodynamic surfaces of an airfoil.
For example, a slat may be located at a leading edge of an airfoil in the form of a wing. A slat is an extension to the front of a wing to provide lift augmentation. Further, a slat may reduce a stalling speed by altering airflow over the wing. Movement of this type of control surface, as well as other control surfaces, during flight may be performed to maximize the handling and performance of the aircraft. For example, a wing may be configured to have a sleek leading edge for high-speed flight. The wing may be reconfigured to have a blunt leading edge for low-speed flight.
When modifying the shape of an airfoil, it is desirable to maintain aerodynamic flow, while minimizing drag and turbulence over the airfoil. One manner in which this characteristic may be achieved is to maintain a contiguous surface on the skin of the airfoil without disruptions around the airfoil in the form of gaps. Current airfoil changing systems for leading edge wings include extension or unfolding mechanisms that protrude into the airstream to modify aerodynamic characteristics. These types of systems, however, create voids in the continuity of the skin on the airfoil that can generate turbulence.
Further, other airfoil shape changing systems may allow the leading edge to lower to provide a blunt leading edge to modify the camber, which is the asymmetry between the top and bottom curves of an airfoil and cross section. These types of systems, however, do not allow for a shape change in the leading edge that is simultaneous with a grouping action. As can be seen, with current airfoil change systems, the types of changes to the surface of an airfoil may be limited and/or may generate gaps that reduce aerodynamic performance.
Therefore, it would be advantageous to have a method and apparatus that addresses at least some of the issues discussed above.